diff --git a/SpreadsheetReader_XLSX.php b/SpreadsheetReader_XLSX.php
index 9cf8d12..d9609f3 100644
--- a/SpreadsheetReader_XLSX.php
+++ b/SpreadsheetReader_XLSX.php
@@ -929,7 +929,7 @@ private function FormatValue($Value, $Index)
 		public function GeneralFormat($Value)
 		{
 			// Numeric format
-			if (is_numeric($Value))
+            if (is_numeric($Value) && preg_match('/^(?:-)?([1-9]|(0\.))/', $Value))
 			{
 				$Value = (float)$Value;
 			}